PKR inhibition prevents maladaptive responses to endoplasmic reticulum (ER) stress in early-onset dystonia DYT-PRKRA.

DYT-PRKRA is a rare, childhood-onset dystonia caused by mutations in the PRKRA gene, which encodes the protein PACT. PACT activates protein kinase R (PKR) in response to endoplasmic reticulum (ER) stress. In DYT-PRKRA patient cells, the PACT-PKR interaction is enhanced, increasing sensitivity to ER stress-induced apoptosis. The canonical protein kinase activated by ER stress is PKR-like endoplasmic reticulum kinase (PERK), which phosphorylates the subunit of eukaryotic translation initiation factor 2 (eIF2) to initiate the integrated stress response (ISR) and restore cellular homeostasis via the transcription factor ATF4. However, under persistent stress, ATF4 induces CHOP, shifting the adaptive response toward apoptosis. PKR, also activated by ER stress, phosphorylates eIF2, but its contribution to cellular homeostasis remains understudied. This work shows, for the first time, that PKR activation is essential for CHOP induction during ISR, directly linking enhanced apoptosis in DYT-PRKRA cells to prolonged PKR activation and heightened CHOP induction. Strikingly, a small-molecule PKR inhibitor effectively blocks CHOP expression and significantly decreases apoptosis in DYT-PRKRA cells, suggesting PKR inhibition as an effective therapeutic strategy for DYT-PRKRA.